Space Exploration:
- September 1: The spacecraft Mars Polar Lander was launched by NASA to study the planet Mars's polar regions.
Technology:
- September 2: The first version of the popular instant messaging software called ICQ (I Seek You) was released.
- September 5: The first version of the video-sharing platform Vimeo was launched.
- September 17: The first iMac with the new "Fruit-Colored" designs and an iBook were unveiled by Apple.
Natural Disasters:
- September 21: A strong earthquake measuring 7.6 on the Richter scale struck Taiwan, causing significant damage and loss of life.
Entertainment:
- September 8: The popular sitcom "Scrubs" premiered on NBC, starring Zach Braff and Donald Faison.
Sports:
- September 11: The US Open Tennis Championships concluded, with Andre Agassi and Serena Williams winning the men's and women's singles titles, respectively.
- September 19: Venus Williams won the US Open Tennis Championships, defeating Lindsay Davenport in the women's singles final.
World News:
- September 14: The body of the former Chilean dictator Augusto Pinochet was exhumed from a cemetery to confirm his identity amid accusations of human rights violations during his regime.
- September 21: Taiwan held its first presidential election in which opposition leader Chen Shui-bian won.
Music:
- September 21: The music group Destiny's Child released their second studio album, "The Writing's on the Wall," featuring hit singles like "Say My Name" and "Jumpin', Jumpin'."
Awards:
- September 12: The 51st Primetime Emmy Awards recognized the best in television productions during 1998-1999, with "The Sopranos" winning Outstanding Drama Series.
Politics:
- September 24: Olusegun Obasanjo was sworn in as the president of Nigeria, ending the country's military rule.
These are just a few of the notable events that occurred in September 1999.